This invention relates to new catalytic asymmetric hydrogenation processes. More specifically, this invention is directed to a hydrogenation process which provides excellent levels of optical purity.
Homogeneous catalysis, i.e., those catalyzed reactions that are conducted where both reactants and catalysts are soluble in the reaction mass, have been found to be particularly useful in processes wherein an asymmetric result is obtained. For instance, it has been found that when an olefin, which is capable of forming a racemic mixture is hydrogenated in the presence of a homogeneous, optically active catalyst, one or the other of the possible optical enantiomorphs is obtained in a major amount with the other optical enantiomorph being obtained in minor amounts. Furthermore, it has been found that certain such olefinic substrates, for instance, precursors of .alpha.-amino acids containing .alpha.-acrylamido substituents, are particularly amenable to hydrogenation with homogeneous, optically active catalysts. Such catalytic asymmetric hydrogenation processes have resulted in the production of large amounts of the desired optical enantiomorph. It has more recently been found that certain homogeneous, optically active catalysts containing optically active bis phosphine ligands provide excellent levels of optical purity, reaching 80% and higher with such .alpha.-amino acid precursors. Other olefinic substrates which would provide excellent levels of optical purity, upon hydrogenation, are particularly desirable.
It is an object of the present invention to provide such olefinic substrates.
It is a further object to provide novel catalytic asymmetric hydrogenation processes which produce large amounts of the desired optical enantiomorph.
These and other objects, aspects and advantages of this invention will become apparent from a consideration of the accompanying specification and claims.